1. Field of the Invention
The present invention is directed to an attachment for a microscope which imparts improved resolution and which allows a high precision and efficient imaging of a specimen.
2. Discussion of the Background
Confocal microscopy is established as a technique used in a great number of laboratories. Confocal optical microscopes, and particularly scanning confocal optical microscopes, are known for having an extremely short depth of focus and improved transverse resolution. A confocal optical microscope includes an internal light source to illuminate an object.
Confocal microscopes, however, are very expensive any may have only certain limited applications. Therefore, it would be beneficial to provide a confocal attachment to a standard microscope which would allow confocal microscopy in conjunction with the standard microscope. Such a confocal attachment would have its own internal light source. One example of such a background confocal attachment is the Zeiss CSM shown schematically in FIG. 4.
The confocal attachment of FIG. 4 connects to a standard optical microscope and includes a tube head 141 as an output viewing point with certain optical elements. The standard optical microscope is shown as elements 161-163 in FIG. 4. Element 162 is a tube lens which focuses light onto a specimen 163. Light reflected off the specimen 163 is output to a standard viewing point 161 of the standard microscope.
The confocal attachment of FIG. 4 provides a way to illuminate the specimen 163 from light output from a light source 149. The specimen 163 can then be viewed at the output of the tube head 141 or at a television output 145 through a TV selector 147
With this confocal attachment, light is output from the light source 149, which for example may be a halogen or HBO light source. The output light from light source 149 passes through a motorized aperture diaphragm 151 and a filter 153. The output light then continues and passes through a focusing lens 156. The light passing through this focusing lens 156 then impinges on a motorized beam splitter 155 which is designed to reflect the output light from the light source 149 towards a removable spinning disk 157. The lens 156 is chosen such that the light output from the light source 149 focuses onto the removable spinning disk 157. The light focused on the spinning disk 157 then passes through the removable spinning disk 157 to reflect off an autofocus sensor 159 (which is optional). The light then reflects off the autofocus sensor 159 through a tube lens 162 to impinge on a sample 163.
The reflected light off of sample 163, which is an image of the sample 163, then follows a return path through tube lens 162, off the autofocus sensor 159, to be again focused on the spinning disk 157. This reflected light then passes through the motorized beam splitter 155 (beam splitter 155 is designed to pass the reflected excitation light from sample 163, which is at a different wavelength than the emission light output from light source 149), through a further beam splitter 143, and through further optical elements to the tube head 141 where the image of the sample can then be viewed.
This confocal attachment for a standard microscope as shown in FIG. 4, however, suffers from some significant drawbacks.
First, this confocal attachment focuses the emission light output from the light source 149 onto the spinning disk 157 through focusing lens 156. This ensures that the emission light is focused on a spinning disk 157, but also results in introducing the focusing lens 156 through which significant optical transmission losses arise.
Further, a drawback with the confocal attachment of FIG. 4, and other confocal microscopes, is chromatic aberration. In confocal microscopy, since sub-micron dimensions are being imaged, chromatic aberration (i.e. the diffraction of the color components of a light source by different amounts) becomes a significant problem. Chromatic aberration is introduced any time that a light source is focused. In the confocal attachment of FIG. 4, light from the light source 149 is focused by both focusing lens 156 and tube lens 162. As a result, two instances of introducing chromatic aberration result in the confocal attachment of FIG. 4. Correcting such chromatic aberration requires rendering the optics in the confocal attachment of FIG. 4 more complicated.
Further, the confocal attachment of FIG. 4 includes a complicated and lengthy optical path including several optical elements provided for propagating the light generated from the light source 149 and propagating the light reflected off the sample 163. The use of such a large number of optical elements results in great optical transmission loss in the imaging of the sample.